(i) Field of the Invention
The invention relates to amphetamine compounds, compositions and methods of delivery and use comprising amphetamine covalently bound to a chemical moiety.
The invention relates to compounds comprised of amphetamine covalently bound to a chemical moiety in a manner that diminishes or eliminates pharmacological activity of amphetamine until released. The conjugates are stable in tests that simulate procedures likely to be used by illicit chemists in attempts to release amphetamine. The invention further provides for methods of therapeutic delivery of amphetamine compositions by oral administration. Additionally, release of amphetamine following oral administration occurs gradually over an extended period of time thereby eliminating spiking of drug levels. When taken at doses above the intended prescription, the bioavailability of amphetamine, including peak levels and total amount of drug absorbed, is substantially decreased. This decreases the potential for amphetamine abuse which often entails the use of extreme doses (1 g or more a day). The compositions are also resistant to abuse by parenteral routes of administration, such as intravenous “shooting”, intranasal “snorting”, or inhalation “smoking”, that are often employed in illicit use. The invention thus provides a stimulant based treatment for certain disorders, such as attention deficit hyperactivity disorder (ADHD), which is commonly treated with amphetamine. Treatment of ADHD with compositions of the invention results in substantially decreased abuse liability as compared to existing stimulant treatments.
(ii) Background of the Invention
The invention is directed to amphetamine conjugate compounds, compositions, and methods of manufacture and use thereof. In particular, the invention is directed to an anti-abuse/sustained release formulation which maintains its therapeutic effectiveness when administered orally. The invention further relates to formulations which diminish or reduce the euphoric effect while maintaining therapeutically effective blood concentrations following oral administration.
Amphetamine is prescribed for the treatment of various disorders, including attention deficit hyperactivity disorder (ADHD), obesity and narcolepsy. Amphetamine and methamphetamine stimulate the central nervous system and have been used medicinally to treat ADHD, narcolepsy and obesity. Because of its stimulating effects amphetamine and its derivatives (e.g., amphetamine analogs) are often abused. Similarly, p-methoxyamphetamine, methylenedioxyamphetamine, 2,5-dimethoxy-4-methylamphetamine, 2,4,5-trimethoxyamphetamine and 3,4-methylenedioxymethamphetamine are also often abused.
In children with attention deficit hyperactivity disorder (ADHD), potent CNS stimulants have been used for several decades as a drug treatment given either alone or as an adjunct to behavioral therapy. While methylphenidate (Ritalin) has been the most frequently prescribed stimulant, the prototype of the class, amphetamine (alpha-methyl phenethylamine) has been used all along and increasingly so in recent years. (Bradley C, Bowen M, “Amphetamine (Benzedrine) therapy of children's behavior disorders.” American Journal of Orthopsychiatry 11: 92) (1941).
The potential for abuse of amphetamines is a major drawback to its use. The high abuse potential has earned it Schedule II status according to the Controlled Substances Act (CSA). Schedule II classification is reserved for those drugs that have accepted medical use but have the highest potential for abuse. The abuse potential of amphetamine has been known for many years and the FDA requires the following black box warning in the package inserts of products:
Furthermore, recent developments in the abuse of prescription drug products increasingly raise concerns about the abuse of amphetamine prescribed for ADHD. Similar to OxyContin, a sustained release formulation of a potent narcotic analgesic, Adderall XR® represents a product with increased abuse liability relative to the single dose tablets. The source of this relates to the higher concentration of amphetamine in each tablet and the potential for release of the full amount of active pharmaceutical ingredient upon crushing. Therefore, like OxyContin, it may be possible for substance abusers to obtain a high dose of the pharmaceutical with rapid onset by snorting the powder or dissolving it in water and injecting it. (Cone, E. J., R. V. Fant, et al., “Oxycodone involvement in drug abuse deaths: a DAWN-based classification scheme applied to an oxycodone postmortem database containing over 1000 cases.” J Anal Toxicol 27(2): 57–67; discussion 67) (2003).
It has been noted recently that “53 percent of children not taking medication for ADHD knew of students with the disorder either giving away or selling their medications. And 34 percent of those being treated for the disorder acknowledged they had been approached to sell or trade them.” (Dartmouth-Hitchcock, 2003) “Understanding ADHD Stimulant Abuse.” http://12.42.224.168/healthyliving/familyhome/jan03familyhomestimulantabuse.htm). In addition, it was reported that students at one prep school obtained Dexedrine and Adderall to either swallow tablets whole or crush and sniff them. (Dartmouth-Hitchcock (2003).
According to the drug enforcement administration (DEA, 2003):                Methylphenidate and amphetamine can be abused orally or the tablets can be crushed and snorted or dissolved in water and injected. The pattern of abuse is characterized by escalation in dose, frequent episodes of binge use followed by severe depression and an overpowering desire to continue the use of these drugs despite serious adverse medical and social consequences.        Rendering this potent stimulant resistant to abuse, particularly by parenteral routes such as snorting or injecting, would provide considerable value to this otherwise effective and beneficial prescription medication.        (DEA (2003). “Stimulant Abuse By School Age Children: A Guide for School Officials. ”http://www.deadiversion.usdoj.gov/pubs/brochures/stimulant/stimulant13abuse.htm).        
Typically, sustained release formulations contain drug particles mixed with or covered by a polymer material, or blend of materials, which are resistant to degradation or disintegration in the stomach and/or in the intestine for a selected period of time. Release of the drug may occur by leaching, erosion, rupture, diffusion or similar actions depending upon the nature of the polymer material or polymer blend used. Additionally, these formulations are subject to breakdown following relatively simple protocols which allows for abuse of the active ingredient.
Conventionally, pharmaceutical manufacturers have used hydrophilic hydrocolloid gelling polymers such as hydroxypropyl methylcellulose, hydroxypropyl cellulose or Pullulan to formulate sustained release tablets or capsules. These polymers first form a gel when exposed to an aqueous environment of low pH thereby slowly diffusing the active medicament which is contained within the polymer matrix. When the gel enters a higher pH environment such as that found in the intestines, however, it dissolves resulting in a less controlled drug release. To provide better sustained release properties in higher pH environments, some pharmaceutical manufacturers use polymers which dissolve only at higher pHs, such as acrylic resins, acrylic latex dispersions, cellulose acetate phthalate, and hydroxypropyl methylcellulose phthalate, either alone or in combination with hydrophilic polymers.
These formulations are prepared by combining the medicament with a finely divided powder of the hydrophilic polymer, or the hydrophilic and water-insoluble polymers. These ingredients are mixed and granulated with water or an organic solvent and the granulation is dried. The dry granulation is then usually further blended with various pharmaceutical additives and compressed into tablets.
Although these types of formulations have been successfully used to manufacture dosage forms which demonstrate sustained release properties, these formulations are subject to several shortcomings including uneven release and are subject to abuse.
The need exists for an abuse resistant dosage form of amphetamine which is therapeutically effective. Further, the need exists for an amphetamine dosage form which provides sustained release and sustained therapeutic effect.